It is the usual practice to change the length of stitch loops being formed on a multi-feed circular knitting machine by vertically adjusting the individual stitch cams at each of the yarn feeding and knitting stations to provide a vertical adjustment of the operating paths of the knitting needles to produce a knit fabric of a desired density. Adjusting the vertical position of the individual knitting cams is quite time consuming and requires a highly skilled operator in order to insure that all of the knitting stations are producing stitch loops of the same length.
This type of individual stitch length control adjustment is particularly difficult when using compound needles where the adjustment of the path of travel of the needles may extend beyond the normal feeding position of the yarn guides at the particular knitting station. Therefore, the changing of the stitch density of the fabric also requires individual adjustment of the yarn guide positions to correspond with the change in the path of travel of the needles. This individual adjustment of the position of the yarn guides at each of the knitting stations is also time consuming and requires a skilled operator. The larger the number of yarn feeders and yarn guides associated with the knitting machine, the longer the time required to change the individual stitch cams and the yarn feeding fingers or guides at each knitting station.
In order to solve the problem of providing individual adjustment of the stitch cams and the yarn guides at each knitting station, it has been proposed to provide a central control apparatus for the simultaneous adjustment of the stitch length and the position of the yarn guides at each knitting station by providing a threaded outer peripheral surface on the inner knitting cam block supporting ring, and a threaded adjustment ring surrounding the inner knitting cam block supporting ring. Rotational movement of the adjustment ring imparts corresponding vertical raising and lowering movement to the inner knitting cam block supporting ring to simultaneously adjust the stitch length being formed at each of the knitting stations. When the yarn carrier ring support and the yarn guides are mounted on the inner knitting cam block supporting ring, they are also simultaneously adjusted as the stitch length is adjusted. This arrangement does provide for simultaneous adjustment of the stitch length and adjustment of the yarn guides. However, a large gear-driving apparatus is required in this device to enable the inner knitting cam block supporting ring to be raised or lowered, and this type of large threaded gear-driving apparatus must have the threaded mating parts manufactured to very close tolerances, thereby increasing the manufacturing costs.